The present invention concerns a sleeve-mounted spike fitted on a vehicle tyre, comprising a rivet, a head, a tip and a sleeve.
The road attrition effect of spiked tyres has been found to be mainly due to the impact action of the spike in the road contact situation and to the scratching effect from the spike when the spike is pressed against the road surface in conditions of load-bearing tyre, and particularly due to the scratching effect at the very moment when the spike is losing road contact.
The impact produced in the road contact situation of the spike results from the kinetic energy of the spike, from the resisting visco-elastic nature of the rubber and from the friction counter-acting the movement of the spike. The impact at first contact and the road attrition effect can therefore be substantially reduced by removing the causative factors of these phenomena. The expedient of reducing the kinetic energy of the spike by reducing its weight is already known in the art. The object of the present invention is to reduce the other harmful effects.
The scratching effect of the spike, as the tyre rolls, is due to the difference between the radius of the wearing surface and the true radius of rotation, this differential giving rise to a slipping tendency of the tyre surface and thereby producing the scratching effect of the spike. The stress from said slipping tendency is discharged just at the moment when the spike contact ends, and at this time the scratching effect is also at its maximum.